The present invention relates to a mounting arrangement for a roller used in the processing of an elongated piece of material. In particular, the invention has application in the support for rollers used in the manufacture of welded steel pipes.
For many years, steel pipe has been produced by bending a sheet of steel into a tubular form and then welding the edges of the strip along a seam. Equipment utilizing various series of breakdown rolls, cage rolls and fin-pass rolls are in widespread use. For example, reference may be made to U.S. Pat. No. 5,140,123 which shows a method and apparatus for continuously manufacturing a metal tube. An earlier example of such machinery and techniques is shown in U.S. Pat. No. 4,709,845. Refinements of the types of machines shown in the foregoing patents are described in U.S. Pat. Nos. 5,607,098; 5,673,579; and 5,784,911.
In traditional tube forming machinery in which rollers of various shapes are used to bend sheet steel into a tubular shape, it has been assumed that the precise position of each roller should be set and held fixed. In conventional machines, the horizontal and vertical location of the rolls, along with the angular position of the axis of the forming rolls, has been adjusted and set to a specific value depending upon such factors as the particular thickness of the sheet being processed, the type of steel (i.e., stainless, etc.), the hardness and quality of the material, and the shape of the desired end product. In situations where the steel is to be processed through the tube forming machines is of lower and more variable quality, the fixed position of the rolls can create difficulties relating to twisting, excessive loading of the rollers, threading of the strip through the machine and marking of the surface of the steel processed by the machine. If the steel processed by the machine varies from sheet to sheet because, for example, of variations in the processes used to make the steel which comprises the sheet, such variations can create significant handling difficulties when such sheets arc used to make tubes.
Variations in properties such as hardness and surface characteristics may mean that frequent adjustments in the positions of the rolls used to process such material are required. In a continuous tube forming process, stoppage of the process to adjust the positions of the forming rolls is quite problematic. As an alternative to stopping the machine in order to make adjustments, forcing the material through the machine can result in excessive loading of the rolls, resulting in excessive wear of both the rolls and the bearings for the rolls, and the creation of roll marks on the surface of the tube being processed.
Another difficulty associated with the use of rolls with positions which are fixed is that threading of the sheet through the machine for purposes of initial start-up can be difficult, particularly where the material of the sheet has inconsistencies in the properties of the material. With certain materials, the sheet when held by fixed rolls will tend to twist and distort, making threading of the sheet through the machine very difficult.
At least some of the foregoing problems and disadvantages of conventional tube forming machinery are solved by use of the present invention wherein rolls in the cage zone of a tube forming machine are flexibly supported such that they are free to rotate about a plurality of axes. A roller mount of the present invention includes a typical vertical frame for supporting a cage roll. However, the roller itself is mounted so that it is free to pivot in an X-Y plane. In addition, the roller is mounted on a swivel bearing carried by the main vertical frame so that the angular position of the axis of the roller is free to pivot in a Y-Z plane of the machine, as well, which is explained more fully below.
In machines in which the cage rollers are mounted in pairs, the pair of cage rolls are additionally mounted so that they are free to pivot in an X-Z plane of the machine. Thus, in a conventional tube-forming machine wherein a pair of cage rollers is used, the cage rolls are mounted so that they have freedom of movement about three axes.